Immuno-gold lateral flow assay

Abstract

A chromatographic lateral-flow assay system for rapid, high sensitivity method of detecting low levels of ligands in body fluids, with few false positives and few false negatives. The lateral-flow assay may have a membrane strip in ribbon form, which increases detection on the order of 2 to 10 fold over the conventional chromatographic specific binding assay techniques by placing a dried or lyophilized conjugate in colloidal spheres opposite side of the lateral flow membrane strip. A chromatographic specific binding assay strip device, comprising: a laminate strip having a first side and an opposite second side; a conjugate pad or membrane disposed on said first side of said laminate; a sample receiving pad or membrane strip and reservoir pad or membrane disposed on said second side of said laminate; and a detection pad or membrane strip disposed between the sample pad or membrane and the reservoir pad or membrane on said second side of said laminate. The assay system comprises a housing device, such as a test tube or cassettes to facilitate the mixing of a sample solution with the dried or lyophilized conjugate, and kits.

1. A chromatographic specific binding assay strip device comprising a laminate strip having a first side and an opposite second side, said laminate strip comprising:
 (a) a fibrous conjugate pad comprising a colloidal labeled immunological binding reagent, said fibrous conjugate pad is disposed on said first side of said laminate; said fibrous conjugate pad has a first end and a second end, and is adapted to receiving a liquid sample applied directly thereto; 
 (b) a fibrous sample receiving pad disposed on said second side of the laminate; said fibrous sample receiving pad is in liquid communication with at least the first or second end of the fibrous conjugate pad; 
 (c) a fibrous reservoir pad disposed on the second side of said laminate and 
 (d) a fibrous detection pad disposed between said fibrous sample pad and said fibrous reservoir pad; 
 wherein said sample receiving pad, fibrous detection pad and fibrous reservoir pad are in capillary liquid communication facilitating a unidirectional migration of liquid from the sample receiving pad through the detection pad into the reservoir pad. 
 
     
     
       2. The device of  claim 1  further comprising a cassette wherein said assay strip is encased inside said cassette; said cassette further comprising a sample slot on one side of the cassette for receiving the liquid sample onto the conjugate pad of said assay strip. 
     
     
       3. The device of  claim 1  wherein the sample receiving pad and conjugate pad further comprise blocking agents including bovine serum albumin and detergent. 
     
     
       4. The device of  claim 1 , wherein said detection pad is impregnated with antibody to capture total, class and subclass immunoglobulins. 
     
     
       5. The device of  claim 2 , wherein said cassette contains ridges or further includes channels on the opposite side of said sample slot. 
     
     
       6. A kit comprising the device of  claim 1  and a buffered diluent. 
     
     
       7. A kit comprising the device of  claim 2  and a buffered diluent. 
     
     
       8. A method of detecting the presence or absence of analyte or ligand in a liquid sample comprising the steps of:
 applying the sample liquid to the fibrous conjugate pad of  claim 1 ; 
 allowing the sample to form a mixture comprising analyte-colloidal labeled immunological reagent complexes; 
 allowing the mixture to flow by capillary action from the conjugate pad to the sample receiving pad and the detection pad; 
 detecting the presence or absence of the complexes in the detection pad and relating the presence or absence of the complexes to the presence or absence of the analyte in the test sample. 
 
     
     
       9. The method of  claim 8  wherein the analyte or ligand is selected from the group consisting of proteins, modified proteins, hormones, peptides, drugs, carbohydrates, haptens, and chemicals. 
     
     
       10. The method of  claim 8 , wherein the liquid sample is selected from the group consisting of a bio-fluid, plant extracts, environmental samples, tissue samples and enrichment broths. 
     
     
       11. The method of  claim 8 , wherein the sample is prefiltered to remove heavy loads of a particulate matter. 
     
     
       12. The method of  claim 8 , wherein the analyte is selected from the group consisting of an infectious disease marker, a pregnancy marker, a microbe, an ovulation marker, a cancer marker, an autoimmunity marker, a cardiac marker, a biowarfare agent, an allergy marker, a drug of abuse and an environmental monitoring marker. 
     
     
       13. The method of  claim 10 , wherein the bio-fluid is selected from the group consisting of tissue extracts, blood, serum, plasma, tears, perspiration, urine, and saliva.